What size AC for Grand Forks, ND? 2 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Grand Forks needs

2 tons central AC or heat pump, about 23,200 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 81% more than this climate needs. An oversized unit cools the air fast, shuts off before it pulls moisture out, and leaves the house cold and clammy.

If a contractor quotes you more than 2 tons for an average 2,000 sq ft house here, ask to see the Manual J load calculation behind it before you sign. That works out to one ton per 1,034 square feet in this climate. For a single room, size by the room: 11.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Grand Forks International Airport (4.7 mi away). Jul is the hottest month, averaging a high of 80.7°F and a low of 57°F, with about 9 days a year at 90°F or more. That gives a design temperature of 85°F against 75°F inside.

What it costs to run

About 482 kWh a year at SEER2 14.3, or roughly $60 at North Dakota's average residential rate of 12.46¢ per kWh. Cooling runs 3 months of the year here.

What drives the load in Grand Forks

Of the 23,200 BTU/hr, 7,200 comes through walls, roof and windows on a 85°F afternoon (31%), 13,000 is sun on the house (56%), 2,120 is four people and their appliances, and 900 is moisture the coil has to wring out of Grand Forks's summer air (4%).

Sun is the biggest share here, more than heat through the walls, so shading west windows and a light roof cut the size you need more than extra insulation would. Sensible heat totals 22,320 BTU/hr before the moisture allowance.

Other house sizes in Grand Forks

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,700 BTU/hr; a 350 sq ft living room needs about 4,100 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 7,000 BTU/hr.

Month by month in Grand Forks

Jul alone uses 38% of the year's cooling energy. The unit runs the equivalent of 297 hours a year at full output.

Grand Forks against nearby cities

Of 9 North Dakota cities here, Grand Forks has the lowest cooling load. The range runs from Grand Forks at 23,200 BTU/hr to Minot at 26,400.

Where Grand Forks's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Grand Forks International Airport, 4.7 miles from the center of Grand Forks at 838 ft above sea level. That is close enough that the station's summers are Grand Forks's summers.

No other city in this set uses Grand Forks International Airport, so this sizing is Grand Forks's alone.

The sun over Grand Forks in late July

At 47.92°N, the noon sun on 21 July stands 62.5° above the horizon over Grand Forks and the day runs 15 h 15 min from sunrise to sunset. A lower noon sun puts more of the day's heat on east and west walls than on the roof, which is why shading west glass pays off here. Long days mean the house keeps gaining heat into the evening, well after the outdoor peak.

59,845 people live in Grand Forks, the 3rd largest of the 9 North Dakota cities sized on this site. Coordinates used: 47.9196, -97.0873.

Grand Forks AC sizing questions